In recent years, liquid crystal display device is getting thin and the demand for large-sized liquid crystal display device is getting strong. Because the number of the internal circuits increases with the size of the liquid crystal display device, accordingly more electric power is consumed. For example, a general liquid crystal display device includes a clock generator circuit configured to generate the clock signals for the internal circuits. Specifically, a conventional clock generator circuit is supplied with an external electric power and converts the external power into the high and low voltage levels of the clock signals for the internal circuits. Because the liquid crystal display device has increased size, the clock generator circuit has to provide more and more clock signals; and consequentially, the clock generator circuit as well as the liquid crystal display device consumes more and more electric power. Thus, for a liquid crystal display device, it is important to develop a clock generator circuit consuming less electric power.